Image jaggedness filter for determining whether to perform baseline calculations

Abstract

An image jaggedness filter is disclosed that can be used to detect the presence of ungrounded objects such as water droplets or coins, and delay periodic baseline adjustments until these objects are no longer present. To do otherwise could produce inaccurate normalized baseline sensor output values. The application of a global baseline offset is also disclosed to quickly modify the sensor offset values to account for conditions such as rapid temperature changes. Background pixels not part of any touch regions can be used to detect changes to no-touch sensor output values and globally modify the sensor offset values accordingly. The use of motion dominance ratios and axis domination confidence values is also disclosed to improve the accuracy of locking onto dominant motion components as part of gesture recognition.

What is claimed is: 
     
       1. A method of delaying a periodic baseline adjustment of a plurality of touch sensor outputs on a touch sensor panel until objects having a high spatial frequency have been substantially removed from the touch sensor panel, comprising:
 computing a jaggedness measure for at least a portion of the plurality of touch sensor outputs based on a plurality of computed differences between the portion of the plurality of touch sensor outputs, the plurality of computed differences including differences between each of the touch sensor outputs in the portion and at least one other touch sensor output in the portion; and 
 delaying or performing the periodic baseline adjustment of the plurality of touch sensor outputs based at least in part on the jaggedness measure. 
 
     
     
       2. The method of  claim 1 , further comprising:
 delaying the periodic baseline adjustment of sensor outputs if the jaggedness measure exceeds a first predetermined threshold. 
 
     
     
       3. The method of  claim 1 , further comprising:
 delaying the periodic baseline adjustment of sensor outputs if a positive and negative pixel mix is within a second predetermined threshold, and if the jaggedness measure exceeds a first predetermined threshold. 
 
     
     
       4. The method of  claim 1 , further comprising:
 delaying the periodic baseline adjustment of sensor outputs although the jaggedness measure does not exceed a first predetermined threshold, if a positive and negative pixel mix is within a second predetermined threshold, and a number of positive and negative pixels is changing faster than a third predetermined threshold. 
 
     
     
       5. The method of  claim 1 , further comprising:
 delaying the periodic baseline adjustment of the sensor outputs although the jaggedness measure does not exceed a first predetermined threshold, and although a positive and negative pixel mix is outside a second predetermined threshold, if a number of positive and negative pixels is changing faster than a third predetermined threshold. 
 
     
     
       6. The method of  claim 1 , further comprising:
 performing the periodic baseline adjustment of the sensor outputs if the jaggedness measure does not exceed a first predetermined threshold. 
 
     
     
       7. The method of  claim 1 , further comprising:
 performing the periodic baseline adjustment of sensor outputs although the jaggedness measure exceeds a first predetermined threshold, if a positive and negative pixel mix is outside a second predetermined threshold. 
 
     
     
       8. The method of  claim 1 , further comprising:
 performing the periodic baseline adjustment of sensor outputs if a positive and negative pixel mix is outside a second predetermined threshold, if the jaggedness measure does not exceed a first predetermined threshold, and a number of positive and negative pixels is not changing faster than a third predetermined threshold. 
 
     
     
       9. The method of  claim 1 , further comprising:
 performing the periodic baseline adjustment of the sensor outputs although a positive and negative pixel mix is within a second predetermined threshold, if the jaggedness measure does not exceed a first predetermined threshold, and a number of positive and negative pixels is not changing faster than a third predetermined threshold. 
 
     
     
       10. The method of  claim 1 , further comprising:
 computing the jaggedness measure by computing a jaggedness value for all drive and sense lines in the touch sensor panel, and averaging the jaggedness values. 
 
     
     
       11. The method of  claim 4 , further comprising:
 determining if the number of positive and negative pixels is changing faster than the third predetermined threshold by passing sums of the negative and positive pixels through a low pass filter (LPF) to produce an auto-regressive average, and comparing instantaneous positive and negative pixel values to the average. 
 
     
     
       12. A non-transitory computer-readable storage medium storing program code for delaying a periodic baseline adjustment of a plurality of sensor outputs on a touch sensor panel until objects having a high spatial frequency have been substantially removed from the touch sensor panel, the program code for causing performance of a method comprising:
 determining a jaggedness measure of an obtained image of touch based on a plurality of computed differences between at least a portion of the plurality of touch sensor outputs in the image of touch, the plurality of computed differences including differences between each of the touch sensor outputs in the portion and at least one other touch sensor output in the portion; and 
 delaying or performing the periodic baseline adjustment of the plurality of touch sensor outputs based at least in part on the degree of spatial frequency. 
 
     
     
       13. The non-transitory computer-readable storage medium of  claim 12 , the program code further for delaying the periodic baseline adjustment of the sensor outputs if the jaggedness measure exceeds a first predetermined threshold. 
     
     
       14. The non-transitory computer-readable storage medium of  claim 12 , the program code further for delaying the periodic baseline adjustment of sensor outputs a positive and negative pixel mix is within a second predetermined threshold, and the jaggedness measure exceeds a first predetermined threshold. 
     
     
       15. The non-transitory computer-readable storage medium of  claim 12 , the program code further for delaying the periodic baseline adjustment of sensor outputs although the jaggedness measure does not exceed a first predetermined threshold, if a positive and negative pixel mix is within a second predetermined threshold, and a number of positive and negative pixels is changing faster than a third predetermined threshold. 
     
     
       16. The non-transitory computer-readable storage medium of  claim 12 , the program code further for delaying the periodic baseline adjustment of the sensor outputs although the jaggedness measure does not exceed a first predetermined threshold, and although a positive and negative pixel mix is outside a second predetermined threshold, if a number of positive and negative pixels is changing faster than a third predetermined threshold. 
     
     
       17. The non-transitory computer-readable storage medium of  claim 12 , the program code further for performing the periodic baseline adjustment of the sensor outputs if the jaggedness measure does not exceed a first predetermined threshold. 
     
     
       18. The non-transitory computer-readable storage medium of  claim 12 , the program code further for performing the periodic baseline adjustment of sensor outputs although the jaggedness measure exceeds a first predetermined threshold, if a positive and negative pixel mix is outside a second predetermined threshold. 
     
     
       19. The non-transitory computer-readable storage medium of  claim 12 , the program code further for performing the periodic baseline adjustment of sensor outputs if a positive and negative pixel mix is outside a second predetermined threshold, the jaggedness measure does not exceed a first predetermined threshold, and a number of positive and negative pixels is not changing faster than a third predetermined threshold. 
     
     
       20. The non-transitory computer-readable storage medium of  claim 12 , the program code further for performing the periodic baseline adjustment of the sensor outputs although a positive and negative pixel mix is within a second predetermined threshold, if the jaggedness measure does not exceed a first predetermined threshold, and a number of positive and negative pixels is not changing faster than a third predetermined threshold. 
     
     
       21. The non-transitory computer-readable storage medium of  claim 12 , the program code further for computing the jaggedness measure by computing a jaggedness value for all drive and sense lines in the touch sensor panel, and averaging the jaggedness values. 
     
     
       22. The non-transitory computer-readable storage medium of  claim 15 , the program code further for determining if the number of positive and negative pixels is changing faster than the third predetermined threshold by passing sums of the negative and positive pixels through a low pass filter (LFP) to produce an auto-regressive average, and comparing instantaneous positive and negative pixel values to the average. 
     
     
       23. A mobile telephone including a non-transitory computer-readable storage medium storing program code for delaying a periodic baseline adjustment of a plurality of touch sensor outputs on a touch sensor panel until objects having a high spatial frequency have been substantially removed from the touch sensor panel, the program code for causing performance of a method comprising:
 computing a jaggedness measure for at least a portion of the plurality of touch sensor outputs based on a plurality of computed differences between the portion of the plurality of touch sensor outputs, the plurality of computed differences including differences between each of the touch sensor outputs in the portion and at least one other touch sensor output in the portion; and 
 delaying or performing the periodic baseline adjustment of the plurality of touch sensor outputs based at least in part on the jaggedness measure. 
 
     
     
       24. A media player including a non-transitory computer-readable storage medium storing program code for delaying a periodic baseline adjustment of a plurality of sensor outputs on a touch sensor panel until objects having a high spatial frequency have been substantially removed from the touch sensor panel, the program code for causing performance of a method comprising:
 computing a jaggedness measure for at least a portion of the plurality of touch sensor outputs based on a plurality of computed differences between the portion of the plurality of touch sensor outputs, the plurality of computed differences including differences between each of the touch sensor outputs in the portion and at least one other touch sensor output in the portion; and 
 delaying or performing the periodic baseline adjustment of the plurality of touch sensor outputs based at least in part on the jaggedness measure. 
 
     
     
       25. A personal computer including a non-transitory computer-readable storage medium storing program code for delaying a periodic baseline adjustment of a plurality of sensor outputs on a touch sensor panel, until objects having a high spatial frequency have been substantially removed from the touch sensor panel, the program code for causing performance of a method comprising:
 computing a jaggedness measure for at least a portion of the plurality of touch sensor outputs based on a plurality of computed differences between the portion of the plurality of touch sensor outputs, the plurality of computed differences including differences between each of the touch sensor outputs in the portion and at least one other touch sensor output in the portion; and 
 delaying or performing the periodic baseline adjustment of the plurality of touch sensor outputs based at least in part on the jaggedness measure.